GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Audio Play Icon Headphones Icon Plus Icon Minus Icon Check Icon Print Icon Picture icon Single Arrow Icon Double Arrow Icon Hamburger Icon TV Icon Close Icon Sorted Hamburger/Search Icon
Building Science

The Water Efficiency Rating Score (WERS)

The Green Builder Coalition’s new tool is ready

Reading the rated water flow in gallons per minute and then measuring the flow are both part of the Water Efficiency Rating Score process.
Image Credit: Energy Vanguard

The Green Builder Coalition has been working hard on their Water Efficiency Rating Score — the WERS — for homes. The inaugural WERS training happened in Santa Fe, New Mexico, in March. I was in that class, and I learned a lot.

The program has been in development for the past couple of years. Now it’s ready for prime time.

How the program works

Like the HERS Index for energy efficiency, the WERS is a way to put a number on a home’s water efficiency. It’s a water use modeling tool that allows you to compare one house to another. You have to put in all the data for a home’s water use, and the tool gives you a number, generally between 0 and 100. As with the HERS Index, lower is better. A WERS of zero means you’ve got a net zero water house. That happens only when you capture rainwater.

One of the things you do is measure structural waste. That’s the amount of water that comes out of a faucet or shower while you’re waiting for the hot water to arrive. The photo below (see Image #2 at the bottom of the article) shows the equipment we used in the class to measure water for a shower. It consists of a Ziploc bag, a piece of PVC pipe with a couple of fittings to hold the bag, and a measuring cup. This setup works really well!

When you’re doing a field inspection, you go around and fill out the checklist. The screenshot in Image #4 (below) shows part of the checklist for indoor water efficiency. The first thing you do is put a pressure gauge on a faucet, turn off the water supply to the house, and see if the pressure drops.…

GBA Prime

This article is only available to GBA Prime Members

Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.

Start Free Trial


  1. Jonathan Lawrence CZ 4A New Jersey | | #1

    Thanks for the info.


    Thanks for the info. One more index I need to think of on my next build.

    I recently installed an Evolve showered in the master bath of my current house. This shower is a nightmare as it is about 70 feet from the hot water heater and the piping runs in the ceiling above the garage. The Evolve works as advertised and as soon as hot water arrives, the flow slows to a trickle until you pull the rip cord.

  2. User avater GBA Editor
    Allison A. Bailes III, PhD | | #2

    Response to Jonathan Lawrence
    Glad to hear your Evolve shower performs well. I haven't seen them in action but really like the idea.

  3. Daniel Beideck | | #3

    I also have a Evolve showerhead that I really like. In addition to the water (and energy) savings, there are other advantages. Because you can hear the water flow change as soon as it's warm, you are free to do other things while waiting for the shower and still know the instant it's ready. It's not a big deal if what you're doing takes a little longer than it took the shower to get warm since the flow is very minimal once it is warm until you pull the cord.

Log in or become a member to post a comment.



Recent Questions and Replies

  • |
  • |
  • |
  • |